Method and system for keeping interest alive in a content centric network

ABSTRACT

One embodiment provides a system that facilitates a content requesting device to handle a potential timeout event. During operation, the system receives, by a content producing device, a packet that corresponds to a first Interest message from a content requesting device, where the first Interest includes a name. Responsive to determining that additional time is required to generate a matching Content Object for the first Interest, the system generates a notification message which indicates a time period after which a second Interest is to be sent out by the content requesting device. The name for the second Interest can be the same as the name for the first Interest or a new name as indicated in the notification message. The system transmits the notification message to the content requesting device, thereby facilitating the content requesting device to handle a potential timeout event.

RELATED APPLICATION

The subject matter of this application is related to the subject matterin the following applications:

-   -   U.S. patent application Ser. No. 13/847,814, entitled        “ORDERED-ELEMENT NAMING FOR NAME-BASED PACKET FORWARDING,” by        inventor Ignacio Solis, filed 20 Mar. 2013 (hereinafter “U.S.        patent application Ser. No. 13/847,814”); and    -   U.S. patent application Ser. No. 12/338,175, entitled        “CONTROLLING THE SPREAD OF INTERESTS AND CONTENT IN A CONTENT        CENTRIC NETWORK,” by inventors Van L. Jacobson and Diana K.        Smetters, filed 18 Dec. 2008 (hereinafter “U.S. patent        application Ser. No. 12/338,175”);        the disclosures of which are herein incorporated by reference in        their entirety.

BACKGROUND

Field

This disclosure is generally related to distribution of digital content.More specifically, this disclosure is related to providing notificationby a content producing device to a content requesting device of apotential timeout event in order to keep an Interest alive in a contentcentric network (CCN).

Related Art

The proliferation of the Internet and e-commerce continues to create avast amount of digital content. Content-centric network (CCN)architectures have been designed to facilitate accessing and processingsuch digital content. A CCN includes entities, or nodes, such as networkclients, forwarders (e.g., routers), and content producers, whichcommunicate with each other by sending Interest packets for variouscontent items and receiving Content Object packets in return. CCNInterests and Content Objects are identified by their unique names,which are typically hierarchically structured variable lengthidentifiers (HSVLI). An HSVLI can include contiguous name componentsordered from a most general level to a most specific level. As anInterest packet is routed through the network from a content requestingnode to a content producing node, each intermediate CCN router adds anentry in its Pending Interest Table (PIT) corresponding to the Interestand forwards the Interest to the next CCN router. When a matchingContent Object packet is sent from the content producing node back tothe requesting node, it follows the reverse path of the Interest. Eachintermediate CCN router forwards the Content Object along the requestinginterfaces listed in the corresponding PIT entry and subsequentlyremoves the PIT entry, indicating that the Interest has been fulfilled.

A PIT entry can also be removed by a CCN node (or router) when the PITentry times out. A node can select any time out value that the nodedeems appropriate upon adding an Interest to its PIT. PIT entries cantime out under different scenarios. One case is due to congestion in thenetwork, which results in the system dropping the Interest or thematching Content Object. Another case is when the content producing nodeor application responsible for generating the matching Content Objectneeds to perform a computationally intensive task (e.g., that takes 45seconds) before it can send a response back. In both cases, PIT entrytimeouts can lead to the requesting node re-expressing the Interest,sometimes repeatedly and over a short period of time. PIT entry timeoutscan also cause intermediate CCN routers to transmit the re-expressedInterests on multiple interfaces, thus increasing network traffic andcreating additional congestion.

SUMMARY

One embodiment provides a system that facilitates a content requestingdevice to handle a potential timeout event. During operation, the systemreceives, by a content producing device, a packet that corresponds to afirst Interest message from a content requesting device, where the firstInterest includes a name. Responsive to determining that additional timeis required to generate a matching Content Object for the firstInterest, the system generates a notification message which indicates atime period after which a second Interest is to be sent out by thecontent requesting device. The name for the second Interest can be thesame as the name for the first Interest or a new name as indicated inthe notification message. The system transmits the notification messageto the content requesting device, thereby facilitating the contentrequesting device to handle a potential timeout event.

In some embodiments, the notification message further indicates a namefor the second Interest to be sent out, where the name for the secondInterest is identical to or different from the name for the firstInterest.

In some embodiments, the notification message is a Content Object,thereby facilitating an intermediate router to remove an entry in itsPending Interest Table (PIT) corresponding to the first Interest.

In some embodiments, the notification message further indicates that thecontent producing device is generating the content in response to thefirst Interest.

In some embodiments, the content producing device receives a packet thatcorresponds to the second Interest. Responsive to determining that amatching Content Object for the second Interest is available, the systemgenerates a matching Content Object in response to the second Interest,where the matching Content Object contains as payload the contentcorresponding to the first Interest. Furthermore, responsive todetermining that a matching Content Object for the second Interest isnot available, the system generates an additional notification messagewhich indicates a time period after which a third Interest is to be sentout by the content requesting device.

In some embodiments, the system generates, by a content requestingdevice, a packet that corresponds to a first Interest message, where thefirst Interest includes a name. The system transmits the first Interestto a content producing device. The system receives a notificationmessage which indicates a time period after which a second Interest isto be sent out. Responsive to reaching an expiration of the time periodindicated in the notification message, the system generates a packetthat corresponds to the second Interest message. The system receives amatching Content Object in response to the second Interest, therebyfacilitating the content requesting device to handle a potential timeoutevent.

In some embodiments, the content requesting device, responsive totransmitting the second Interest, receives an additional notificationmessage which indicates a time period after which a third Interest is tobe sent out.

In some embodiments, the content requesting device transmits the secondInterest, where the second Interest includes the name indicated in thenotification message.

In some embodiments, the content requesting device removes an entry froma Pending Interest Table (PIT), where the entry corresponds to the firstInterest.

In some embodiments, the content requesting device creates an entry in aPIT, where the entry corresponds to the second Interest.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary network that facilitates a contentrequesting device to handle a potential timeout event, in accordancewith an embodiment of the present invention.

FIG. 2 illustrates exemplary communication between a content requestingdevice and a content producing device, in accordance with an embodimentof the present invention.

FIG. 3 presents a flow chart illustrating a method by a contentrequesting device for processing content, in accordance with anembodiment of the present invention.

FIG. 4 presents a flow chart illustrating a method by a contentproducing device for processing an Interest packet that requiresadditional time to create a matching Content Object, in accordance withan embodiment of the present invention.

FIG. 5A illustrates an exemplary format of a first CCN Interest messageand a notification message, in accordance with an embodiment of thepresent invention.

FIG. 5B illustrates an exemplary format of a second CCN Interest messageand a matching CCN Content Object, in accordance with an embodiment ofthe present invention.

FIG. 6 illustrates an exemplary computer and communication system thatfacilitates a content requesting device to handle a potential timeoutevent, in accordance with an embodiment of the present invention.

In the figures, like reference numerals refer to the same figureelements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the embodiments, and is provided in the contextof a particular application and its requirements. Various modificationsto the disclosed embodiments will be readily apparent to those skilledin the art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present disclosure. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

Overview

Embodiments of the present invention provide a system which facilitateshandling a potential timeout event when a content producing device(e.g., a server) requires additional time to generate a matching ContentObject in response to an Interest from a content requesting device(e.g., a client). During operation, a content producer receives a firstInterest message from a content requester and determines that additionaltime is needed to generate the matching Content Object. The contentproducer sends a notification message to the content requester andincludes an estimate of how long the computation will take, along with aname to be used in a subsequently transmitted second Interest. Thenotification message can be a Content Object whose name is the same asor different from the name for the first Interest message. As thenotification message travels back through the network, each intermediaterouter forwards the Content Object on the reverse path as the firstInterest and removes the corresponding entry from its Pending InterestTable (PIT). The content requester receives the notification message andkeeps track of the time duration. Upon expiration of the time duration,the content requester sends the second Interest, using the name providedin the notification message. The content producer then transmits aContent Object with the second Interest name back to the contentrequester. The matching Content Object contains as payload the contentmatching the first Interest. As the Content Object travels back throughthe network, each intermediate router forwards the Content Object on thereverse path as the second Interest and removes the corresponding entryfrom its PIT.

The content producer is responsible for notifying the content requesterthat generation of the responsive Content Object is in progress.Intermediate CCN routers do not keep track of the computation progressat the content producer and are not required to maintain the stateassociated with the first Interest for the duration of the computationtime. Thus, the first Interest is “kept alive” through notification bythe content producer to the content requester and the appropriatelydelayed second Interest sent out by the content requester. This solutionreduces the amount of unnecessary PIT entry timeouts and frees PITspaces, which in turn reduces network congestion by reducing the numberof re-expressed Interests transmitted and pending in a CCN.

In CCN, each piece of content is individually named, and each piece ofdata is bound to a unique name that distinguishes the data from anyother piece of data, such as other versions of the same data or datafrom other sources. This unique name allows a network device to requestthe data by disseminating a request or an Interest that indicates theunique name, and can obtain the data independent from the data's storagelocation, network location, application, and means of transportation.The following terms are used to describe the CCN architecture:

Content Object:

A single piece of named data, which is bound to a unique name. ContentObjects are “persistent,” which means that a Content Object can movearound within a computing device, or across different computing devices,but does not change. If any component of the Content Object changes, theentity that made the change creates a new Content Object that includesthe updated content, and binds the new Content Object to a new uniquename.

Unique Names:

A name in a CCN is typically location independent and uniquelyidentifies a Content Object. A data-forwarding device can use the nameor name prefix to forward a packet toward a network node that generatesor stores the Content Object, regardless of a network address orphysical location for the Content Object. In some embodiments, the namemay be a hierarchically structured variable-length identifier (HSVLI).The HSVLI can be divided into several hierarchical components, which canbe structured in various ways. For example, the individual namecomponents parc, home, ccn, and test.txt can be structured in aleft-oriented prefix-major fashion to form the name“/parc/home/ccn/test.txt.” Thus, the name “/parc/home/ccn” can be a“parent” or “prefix” of “/parc/home/ccn/test.txt.” Additional componentscan be used to distinguish between different versions of the contentitem, such as a collaborative document.

In some embodiments, the name can include a non-hierarchical identifier,such as a hash value that is derived from the Content Object's data(e.g., a checksum value) and/or from elements of the Content Object'sname. A description of a hash-based name is described in U.S. patentapplication Ser. No. 13/847,814. A name can also be a flat label.Hereinafter, “name” is used to refer to any name for a piece of data ina name-data network, such as a hierarchical name or name prefix, a flatname, a fixed-length name, an arbitrary-length name, or a label (e.g., aMultiprotocol Label Switching (MPLS) label).

Interest:

A packet that indicates a request for a piece of data, and includes aname (or a name prefix) for the piece of data. A data consumer candisseminate a request or Interest across an information-centric network,which CCN routers can propagate toward a storage device (e.g., a cacheserver) or a data producer that can provide the requested data tosatisfy the request or Interest.

The methods disclosed herein are not limited to CCN networks and areapplicable to other architectures as well. A description of a CCNarchitecture is described in U.S. patent application Ser. No.12/338,175.

Exemplary Network and Communication

FIG. 1 illustrates an exemplary network 100 that facilitates a contentrequesting device to handle a potential timeout event, in accordancewith an embodiment of the present invention. Network 100 can include acontent requesting device 116, a content producing device 118, and arouter or other forwarding device at nodes 102, 104, 106, 108, 110, 112,and 114. A node can be a computer system, an end-point representingusers, and/or a device that can generate Interests or originate content.A node can also be an edge router (e.g., CCN nodes 102 and 114) or acore router (e.g., intermediate CCN routers 104-112).

Content requesting device 116 can generate a first Interest in a pieceof content. Network 100 routes the Interest to CCN router 102, whichadds an entry in its Pending Interest Table (PIT) and forwards theInterest to intermediate CCN router 110. Each CCN router that receivesthe first Interest performs the same actions, adding an entry in its PITand forwarding the first Interest to the next hop in the CCN routingpath (e.g., CCN routers 110, 112, 114). Subsequently, CCN router 114adds an entry in its PIT and forwards the first Interest to contentproducing device 118. Device 118 determines that additional computationtime is needed to generate the matching Content Object, so device 118sends a notification message back to content requesting device 116. Thenotification message can be a Content Object with the same name as thefirst Interest, and can further include a time duration (e.g., 30seconds) which indicates an amount of time after which a second Interestshould be sent out by content requesting device 116. The notificationmessage can also include a new name to use in the second Interest. Asthe notification message travels back to content requesting device 116,each CCN router on the reverse CCN routing path (e.g., CCN routers 114,112, 110, and 102), and subsequently device 116, receives thenotification message and removes the corresponding PIT entry for thefirst Interest.

When the time duration indicated in the notification message elapses,content requesting device 116 sends out the second Interest using thenew name provided in the notification message. The second Interesttravels the same path as the first Interest (e.g., through CCN routers102, 110, 112, and 114) and reaches content producing device 118, whichtransmits the matching Content Object to content requesting device 116back along the same path in the reverse direction. Each intermediaterouter again forwards the matching Content Object to the previous hopnode in the reverse data path and removes the corresponding PIT entryfor the second Interest.

In some embodiments, content requesting device 116 can send out thesecond Interest before the time duration indicated in the notificationmessage has elapsed. In response, if the matching Content Object isavailable, content producing device 118 can transmit the matchingContent Object. Alternatively, content producing device 118 candetermine that additional computation time is still needed to generatethe responsive Content Object. Device 118 can send a second (oradditional) keep-alive notification message that indicates a time periodafter which a third Interest should be sent out by content requestingdevice 116. The second notification message can include a name for thethird Interest which is identical to or different from the name of thesecond Interest. FIG. 2 illustrates exemplary communication 200 betweena content requesting device (e.g., device 116 in FIG. 1) and a contentproducing device (e.g., device 118 in FIG. 1), in accordance with anembodiment of the present invention. The vertical lines beneath contentrequesting device 116 and content producing device 118 indicate passageof time. During operation, content requesting device 116 sends a firstInterest with a name of “/a/b/c/d” to content producing device 118(operation 202). Device 118 determines that additional computation timeis required to generate the matching Content Object, and generates anotification message in the form of a Content Object (operation 204).Device 118 transmits the notification message Content Object with a nameof “a/b/c/d” and additional information to indicate to requesting device116 to keep the first Interest alive by re-expressing the first Interest(as a second Interest) at a later time (operation 206). The notificationmessage includes a message to wait, for example, an additional 30seconds before sending out the second Interest and to use the new nameof “/a/b/c/d1” for the second Interest. Content requesting device 116monitors the time, and, when the duration indicated in the notificationmessage has elapsed, sends a second Interest using the new name of“/a/b/c/d1” as indicated in the notification message (operation 208).Meanwhile, content producing device 118 has successfully completedgeneration of the Content Object matching the first Interest (operation210), so device 118 transmits the matching Content Object back to device116 (operation 212).

Content Requesting Device Processes Content

FIG. 3 presents a flow chart 300 illustrating a method by a contentrequesting device for processing content, in accordance with anembodiment of the present invention. During operation, the systemgenerates, by a content requesting device, a packet that corresponds toa first Interest message (operation 302). The system creates acorresponding PIT entry and transmits the first Interest to a contentproducing device (operation 304). The content requesting device receivesa notification message that indicates a time period after which a secondInterest is to be sent out (operation 306). The notification message canbe in the form of a Content Object and can also include a new name touse for the second Interest. The system removes the corresponding PITentry for the first Interest (operation 308).

The content requesting device determines the expiration of the timeduration indicated in the notification message and generates a packetthat corresponds to the second Interest message (operation 310). Thesecond Interest includes the new name indicated in the notificationmessage. In some embodiments, the second Interest includes the same nameas the first Interest. The system creates a corresponding PIT entry andtransmits the second Interest to the content producing device (operation312). In response to the second Interest, the content requesting devicereceives a Content Object that contains as its payload the contentmatching the first Interest (operation 314). Finally, because the secondInterest has been fulfilled, the system removes the corresponding PITentry for the second Interest (operation 316).

Content Producing Device Notifies Content Requesting Device

FIG. 4 presents a flow chart 400 illustrating a method by a contentproducing device for processing an Interest packet that requiresadditional time to create a matching Content Object, in accordance withan embodiment of the present invention. During operation, the systemreceives, by a content producing device, a packet that corresponds to afirst Interest message (operation 402). The system determines thatadditional time is required to generate a matching Content Object inresponse to the first Interest (operation 404) and generates anotification message that indicates a time period after which a secondInterest is to be sent out (operation 406). The time period indicates anamount of time that the content producing device needs to perform thecomputation required to generate the Content Object. Optionally, thenotification message also includes a name to be used in the secondInterest. The system transmits the notification message to a contentrequesting device (operation 408). After the specified duration of timehas passed, the content producing device receives a packet thatcorresponds to the second Interest and includes the name indicated inthe notification message (operation 410). The content producing device,having completed the necessary computation, generates the Content Objectin response to the second Interest (operation 412). The Content Objectincludes as payload the content corresponding to the first Interest. Thecontent producing device then transmits this Content Object to thecontent requesting device (operation 414).

Note that both the first Interest and the second Interest can travelthrough a network that includes multiple intermediate CCN routers. Eachof these CCN routers adds a corresponding entry in its Pending InterestTable (PIT) for the appropriate Interest and forwards the Interest on tothe next hop in the CCN routing path. Furthermore, both the notificationmessage and the matching Content Object can travel through the samenetwork along a reverse path as the first Interest and the secondInterest, respectively. In one embodiment, upon receiving a notificationmessage from the content producing device, each CCN router on thereverse path removes the corresponding entry in its PIT. Thus,notification from the content producing device to the content requestingdevice allows the system to “keep alive” the first Interest through theresulting and appropriately delayed second Interest, while freeing thePIT spaces in the intermediate CCN routers.

Exemplary Format of First CCN Interest and Notification Message

FIG. 5A illustrates an exemplary format of a first CCN Interest message500 and a notification message 520, in accordance with an embodiment ofthe present invention. First Interest 500 includes a name 502 with avalue of “/a/b/c/d.” Notification message 520 includes: a name 522 witha value of “/a/b/c/d” which is the same as name 502 of first Interest500; a wait duration 524 field with a value of “30 seconds” whichindicates the time duration after which a content requesting deviceshould transmit a second Interest; and a second Interest name 526 with avalue of “/a/b/c/d1” which is different from name 502 of first Interest500. In some embodiments, second Interest name 526 can have a value thatis identical to the value of name 502 of first Interest 500.

Exemplary Format of Second CCN Interest and Matching Content Object

FIG. 5B illustrates an exemplary format of a second CCN Interest message540 and a matching CCN Content Object 560, in accordance with anembodiment of the present invention. Second Interest 540 includes a name542 with a value of “/a/b/c/d1” which is the same as second Interestname 526 of notification message 520. Matching Content Object 560includes: a name 562 with a value of “/a/b/c/d1” which is the same asname 542 of second Interest 540; and a payload 564 with a value equal tothe content matching first Interest 500 with name 502 of “/a/b/c/d.”

Exemplary Computer and Communication System

FIG. 6 illustrates an exemplary computer and communication system 602that facilitates a content requesting device to handle a potentialtimeout event, in accordance with an embodiment of the presentinvention. Computer and communication system 602 includes a processor604, a memory 606, and a storage device 608. Memory 606 can include avolatile memory (e.g., RAM) that serves as a managed memory, and can beused to store one or more memory pools. Furthermore, computer andcommunication system 602 can be coupled to a display device 610, akeyboard 612, and a pointing device 614. Storage device 608 can store anoperating system 616, a content-processing system 618, and data 630.

Content-processing system 618 can include instructions, which whenexecuted by computer and communication system 602, can cause computerand communication system 602 to perform methods and/or processesdescribed in this disclosure. Specifically, content-processing system618 may include instructions for receiving, by a content producingdevice, a packet that corresponds to a first Interest message from acontent requesting device, where the first Interest includes a name(communication mechanism 620). Content-processing system 618 can alsoinclude instructions for, responsive to determining that additional timeis required to generate a matching Content Object, generating anotification message which indicates a time period after which a secondInterest is to be sent out (notification message mechanism 622).Content-processing system 618 can include instructions for transmittingthe notification message to the content requesting device (communicationmechanism 620). Content-processing system 618 can further includeinstructions for receiving a packet that corresponds to the secondInterest (communication mechanism 620) and, responsive to determiningthat the matching Content Object for the second Interest is available,generating a matching Content Object in response to the second Interest(content generation mechanism 628). Content-processing system 618 caninclude instructions for, responsive to determining that the matchingContent Object for the second Interest is not available, generating anadditional notification message which indicates a time period afterwhich a third Interest is to be sent out by the content requestingdevice (notification message mechanism 622).

Content-processing system 618 can additionally include instructions forgenerating, by a content requesting device, a packet that corresponds toa first Interest message, where the first Interest includes a name(communication mechanism 620). Content-processing system 618 can includeinstructions for transmitting the first Interest to a content producingdevice and receiving a notification message which indicates a timeperiod after which a second Interest is to be sent out (communicationmechanism 620). Content-processing system 618 can also includeinstructions for, responsive to reaching an expiration of the timeperiod indicated in the notification message, generating a packet thatcorresponds to the second Interest message (re-expressed Interestmechanism 624). Content-processing system 618 can include instructionsfor transmitting the second Interest, where the second Interest includesa name which is identical to or different from the name for the firstInterest (communication mechanism 620). Content-processing system 618can include instructions for receiving a matching Content Object inresponse to the second Interest (communication mechanism 620).Content-processing system 618 can also include instructions for,responsive to transmitting the second Interest, receiving an additionalnotification message which indicates a time period after which a thirdInterest is to be sent out (communication mechanism 620).

Content-processing system 618 can further include instructions forremoving an entry from a Pending Interest Table (PIT) where the entrycorresponds to the first Interest (Pending Interest Table mechanism626). Content-processing system 618 can include instructions forcreating an entry in the PIT where the entry corresponds to the secondInterest (Pending Interest Table mechanism 626).

Data 630 can include any data that is required as input or that isgenerated as output by the methods and/or processes described in thisdisclosure. Specifically, data 630 can store at least: a packet thatcorresponds to a first Interest message; a name for the first Interest;a notification message which indicates a time period after which asecond Interest is to be sent out; a wait duration; a name for thesecond Interest; a notification message that is a Content Object; anindicator that the content producing device is generating the content inresponse to the first Interest; a packet that corresponds to the secondInterest and includes a name provided in the notification message; anadditional notification message which indicates a time period afterwhich a third Interest is to be sent out; a name for the third Interest;a packet that corresponds to the third Interest and includes the namefor the third Interest; a Content Object that contains as payloadcontent in response to the first Interest; an entry in a PendingInterest Table (PIT) that corresponds to the first Interest; a PIT entrythat corresponds to the second Interest; and a PIT entry thatcorresponds to the third Interest.

The data structures and code described in this detailed description aretypically stored on a computer-readable storage medium, which may be anydevice or medium that can store code and/or data for use by a computersystem. The computer-readable storage medium includes, but is notlimited to, volatile memory, non-volatile memory, magnetic and opticalstorage devices such as disk drives, magnetic tape, CDs (compact discs),DVDs (digital versatile discs or digital video discs), or other mediacapable of storing computer-readable media now known or later developed.

The methods and processes described in the detailed description sectioncan be embodied as code and/or data, which can be stored in acomputer-readable storage medium as described above. When a computersystem reads and executes the code and/or data stored on thecomputer-readable storage medium, the computer system performs themethods and processes embodied as data structures and code and storedwithin the computer-readable storage medium.

Furthermore, the methods and processes described above can be includedin hardware modules or apparatus. The hardware modules or apparatus caninclude, but are not limited to, application-specific integrated circuit(ASIC) chips, field-programmable gate arrays (FPGAs), dedicated orshared processors that execute a particular software module or a pieceof code at a particular time, and other programmable-logic devices nowknown or later developed. When the hardware modules or apparatus areactivated, they perform the methods and processes included within them.

The foregoing descriptions of embodiments of the present invention havebeen presented for purposes of illustration and description only. Theyare not intended to be exhaustive or to limit the present invention tothe forms disclosed. Accordingly, many modifications and variations willbe apparent to practitioners skilled in the art. Additionally, the abovedisclosure is not intended to limit the present invention. The scope ofthe present invention is defined by the appended claims.

What is claimed is:
 1. A computer-implemented method for forwardingpackets, the method comprising: receiving, by a content producingdevice, a packet that corresponds to a first Interest message from acontent requesting device, wherein the first Interest message includes afirst name for requested content; responsive to determining, by thecontent producing device, that additional time is required to generate amatching Content Object for the first Interest message, generating anotification message which indicates a time period after which a secondInterest message is to be sent out by the content requesting device,wherein the notification message further indicates a second name for thesecond Interest message; transmitting the notification message to thecontent requesting device, which facilitates an intermediate router toremove a first entry in its Pending Interest Table corresponding to thefirst Interest message based on the first name, and to create a secondentry in its Pending Interest Table corresponding to the second Interestmessage based on the second name receiving a packet that corresponds tothe second Interest message; responsive to determining that a matchingContent Object for the second Interest message is available, generatinga matching Content Object in response to the second Interest message,wherein the matching Content Object contains as payload the contentcorresponding to the first Interest message; and responsive todetermining that the matching Content Object for the second Interestmessage is not available, generating an additional notification messagewhich indicates a time period after which a third Interest message is tobe sent out by the content requesting device, wherein the additionalnotification message further indicates a third name for the thirdInterest message, thereby facilitating the content requesting device tohandle a potential timeout event.
 2. The method of claim 1, wherein thesecond name for the second Interest message is identical to or differentfrom the first name for the first Interest message.
 3. The method ofclaim 1, wherein the notification message is a Content Object whichincludes a third name that is a same name as the first name for thefirst Interest message.
 4. The method of claim 1, wherein thenotification message further indicates that the content producing deviceis generating the content in response to the first Interest message. 5.A computer-implemented method for forwarding packets, the methodcomprising: generating, by a content requesting device, a packet thatcorresponds to a first Interest message, wherein the first Interestmessage includes a first name for requested content; transmitting thefirst Interest message to a content producing device; receiving anotification message which indicates a time period after which a secondInterest message is to be sent out, wherein the notification messagefurther indicates a second name for the second Interest message;removing a first entry from a Pending Interest Table, wherein the firstentry corresponds to the first Interest message and is based on thefirst name; responsive to reaching an expiration of the time periodindicated in the notification message, generating a packet thatcorresponds to the second Interest message; creating a second entry inthe Pending Interest Table, wherein the second entry corresponds to thesecond Interest message and is based on the second name; and receiving amatching Content Object in response to the second Interest message,thereby facilitating the content requesting device to handle a potentialtimeout event.
 6. The method of claim 5, further comprising: responsiveto transmitting the second Interest message, receiving an additionalnotification message which indicates a time period after which a thirdInterest message is to be sent out.
 7. The method of claim 5, whereinthe second name for the second Interest message is identical to ordifferent from the first name for the first Interest message.
 8. Themethod of claim 7, further comprising: transmitting the second Interestmessage, wherein the second Interest message includes the second nameindicated in the notification message.
 9. The method of claim 5, whereinthe 2 notification message is a Content Object which includes a thirdname that is a 3 same name as the first name for the first Interestmessage.
 10. A computer system for facilitating forwarding of packets,the system comprising: a processor; and a storage device storinginstructions that when executed by the processor cause the processor toperform a method, the method comprising: receiving, by a contentproducing device, a packet that corresponds to a first Interest messagefrom a content requesting device, wherein the first Interest messageincludes a first name for requested content; responsive to determining,by the content producing device, that additional time is required togenerate a matching Content Object for the first Interest message,generating a notification message which indicates a time period afterwhich a second Interest message is to be sent out by the contentrequesting device, wherein the notification message further indicates asecond name for the second Interest message; and transmitting thenotification message to the content requesting device, which facilitatesan intermediate router to remove a first entry in its Pending InterestTable corresponding to the first Interest message based on the firstname, and to create a second entry in its Pending Interest Tablecorresponding to the second Interest message based on the second name,receiving a packet that corresponds to the second Interest message;responsive to determining that a matching Content Object for the secondInterest message is available, generating a matching Content Object inresponse to 6 the second Interest message, wherein the matching ContentObject contains as payload the content corresponding to the firstInterest message; and responsive to determining that the matchingContent Object for the second Interest message is not available,generating an additional notification message which indicates a timeperiod after which a third Interest message is to be sent out by thecontent requesting device, wherein the additional notification messagefurther indicates a third name for the third Interest message, therebyfacilitating the content requesting device to handle a potential timeoutevent.
 11. The computer system of claim 10, wherein the second name forthe second Interest message is identical to or 4 different from thefirst name for the first Interest message.
 12. The computer system ofclaim 10, wherein the notification message is a Content Object whichincludes a third name that is a same name as the first name for thefirst Interest message.
 13. The computer system of claim 10, wherein thenotification message further indicates that the content producing deviceis generating the content in response to the first Interest message. 14.A computer system for facilitating forwarding of packets, the systemcomprising: a processor; and a storage device storing instructions thatwhen executed by the processor cause the processor to perform a method,the method comprising: generating, by a content requesting device, apacket that corresponds to a first Interest message, wherein the firstInterest message includes a first name for requested content;transmitting the first Interest message to a content producing device;receiving a notification message which indicates a time period afterwhich a second Interest message is to be sent out, wherein thenotification message further indicates a second name for the secondInterest message; removing a first entry from a Pending Interest Table,wherein the first entry corresponds to the first Interest message and isbased on the first name; responsive to reaching an expiration of thetime period indicated in the notification message, generating a packetthat corresponds to the second Interest message; creating a second entryin the Pending Interest Table, wherein the second entry corresponds tothe second Interest message and is based on the second name; andreceiving a matching Content Object in response to the second Interestmessage, thereby facilitating the content requesting device to handle apotential timeout event.
 15. The computer system of claim 14, whereinthe method further comprises: responsive to transmitting the secondInterest message, receiving an additional notification message whichindicates a time period after which a third Interest message is to besent out.
 16. The computer system of claim 14, wherein the second namefor the second Interest message is identical to or 4 different from thefirst name for the first Interest message.
 17. The computer system ofclaim 16, wherein the method further comprises: transmitting the secondInterest message, wherein the second Interest message includes thesecond name indicated in the notification message.
 18. The computersystem of claim 14, wherein the notification message is a Content Objectwhich includes a third name that is a same name as the first name forthe first Interest message.